Hackers have hacked Inputs.io, a Bitcoin wallet service, and made away with 4,100 Bitcoins worth over $1.2 million.

Inputs.io operates a Bitcoin wallet service, whereby owners can send and receive Bitcoins easily and it claims to be the "most secure" wallet ever created.

The website was compromised twice on October 23 and October 26 and hackers made off with 4,100 Bitcoins that were stolen in two attacks.

"Two hacks totaling about 4,100 BTC have left Inputs.io unable to pay all user balances," the company said. "The attacker compromised the hosting account through compromising e-mail accounts - some very old and without phone numbers attached, so it was easy to reset. The attacker was able to bypass 2FA due to a flaw on the server host side."

Inputs.io notified customers this week; however, the hacking incident only affects certain users. Reportedly, some coins belonging to TradeFortress, the founder of Input.io, and CoinLenders were also taken.

"The attacker rented an Australian server to proxy as close to my geographical location so it won't raise alarms with email recoveries," TradeFortress said.

"I'm repaying with all of my personal Bitcoins, as well as remaining cold storage coins on Inputs, which adds up to 1540 BTC," it added.

The company was also able to recover some Bitcoins and customers will get a partial refund; however, Inputs.io does not have sufficient Bitcoins to repay everyone.

"I know this doesn't mean much, but I'm sorry, and saying that I'm very sad that this happened is an understatement," said Inputs.io.

One of the biggest issues facing owners of the digital currency, introduced in 2008, is where to store them. Bitcoin experts recommend keeping the wallet addresses offline on a piece of paper or external hard drive for safe-keeping from hackers.